Cross-linked cellulose for use in absorbent articles is well known and is disclosed as such in EP-A-0.427.316 (Herron), U.S. Pat. No. 5,549,791 (Herron), WO 98/27262 (Westland), or U.S. Pat. No. 6,184,271 (Westland). While cross-linked cellulose fibers exhibit useful properties and have found broad commercial applications, there remains a need for improving such fibers especially with regard to allowing better balancing of brittleness and resiliency properties of such fibers. While stiffness is often desired to allow for maintenance of an open structure such as for improved liquid handling, stiffness is often linked to increased brittleness of the fibers, creating, for example, undesired break up during the transport of the fibers from the fiber making and fiber treatment plant to the fiber user.
In order to improve on these problems, the present invention relates to the application of radiation activatable resins to the cellulose fibers and, upon application of the radiation, to fiber comprising cross-linked radiation activatable resin.
Radiation curable resins are known in the art and have been disclosed in DE-38 36 370 (Hintze; BASF), or U.S. Pat. No. 5,026,806 (Rehmer; BASF), wherein UV cross-linkable materials based on (meth-) acrylic acid ester or co-polymers thereof are described in particular for being used in hotmelt (contact) adhesives and sealing compounds. Application of photo-curable resins to optical fibers has been disclosed e.g., in WO 99/30843, and the application to non-woven webs is described in U.S. Pat. No. 4,748,044. Further, photocurable, cellulose based compositions are known, which are derived from cellulose based materials, such as described in JP2298501 (Shin Etsu), or JP-08006252 (Sony), the latter relating to a general-purpose photosensitive resin composition. In U.S. Pat. No. 6,090,236 (Nohr), a process is described to create coatings for a web by radiation induced polymerization of monomeric or oligimeric materials.
However, so far it has not been contemplated to exploit radiation induced cross-linking of polymeric material in the context of cellulosic fibers.
Henceforth, the present invention aims at providing cellulose based fibers comprising a radiation activatable cross-linking or curing resin, at structures and especially absorbent articles comprising such fibers, as well as at the methods of making such fibers or structures.
In a particular embodiment, the present invention provides an improved process for handling cellulosic fiber material, especially when this fiber material is being transported or stored during the overall handling, with improved fiber properties resulting from such handling as compared to conventional transporting or storage.